title: Prospective motion correction using inductively coupled wireless RF coils.
abstract: OBJECTIVE
  A novel prospective motion correction technique for brain MRI is presented that uses miniature wireless radio-frequency coils, or "wireless markers," for position tracking.
  
  
  METHODS
  Each marker is free of traditional cable connections to the scanner. Instead, its signal is wirelessly linked to the MR receiver via inductive coupling with the head coil. Real-time tracking of rigid head motion is performed using a pair of glasses integrated with three wireless markers. A tracking pulse-sequence, combined with knowledge of the markers' unique geometrical arrangement, is used to measure their positions. Tracking data from the glasses is then used to prospectively update the orientation and position of the image-volume so that it follows the motion of the head.
  
  
  RESULTS
  Wireless-marker position measurements were comparable to measurements using traditional wired radio-frequency tracking coils, with the standard deviation of the difference < 0.01 mm over the range of positions measured inside the head coil. Wireless-marker safety was verified with B1 maps and temperature measurements. Prospective motion correction was demonstrated in a 2D spin-echo scan while the subject performed a series of deliberate head rotations.
  
  
  CONCLUSIONS
  Prospective motion correction using wireless markers enables high quality images to be acquired even during bulk motions. Wireless markers are small, avoid radio-frequency safety risks from electrical cables, are not hampered by mechanical connections to the scanner, and require minimal setup times. These advantages may help to facilitate adoption in the clinic.
authors.affiliation: Department of Radiology, Stanford University, Stanford, California, USA.
authors.forename: Melvyn B
authors.initials: MB
authors.lastname: Ooi
authors.forename: Murat
authors.initials: M
authors.lastname: Aksoy
authors.forename: Julian
authors.initials: J
authors.lastname: Maclaren
authors.forename: Ronald D
authors.initials: RD
authors.lastname: Watkins
authors.forename: Roland
authors.initials: R
authors.lastname: Bammer
mesh_terms: D001921:Brain / Q000502:physiology*; D004867:Equipment Design; D006257:Head; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D009038:Motion
keywords: active marker; inductive coupling; motion tracking; prospective real‐time motion correction; radio frequency coil; wireless marker